CALIFORNIA 
AGRICULTURAL  EXTENSION  SERVICE 

CIRCULAR  7 
DECEMBER,  1926 


Suggestions  on  Grapefruit  Culture 
in  Imperial  Valley 


RAYMOND   ELLIS 


PUBLISHED  BY 

THE  COLLEGE  OF  AGRICULTURE 

UNIVERSITY  OF  CALIFORNIA 


Cooperative  Extension  work  in  Agriculture  and  Home  Economics,  College  of  Agriculture, 
University  of  California,  and  United  States  Department  of  Agriculture  cooperating.  Dis- 
tributed in  furtherance  of  the  Acts  of  Congress  of  May  8  and  June  30,  1914.  B.  H.  Crocheron, 
Director,  California  Agricultural  Extension  Service. 


UNIVERSITY  OF  CALIFORNIA  PRINTING  OFFICE 

BERKELEY,  CALIFORNIA 

1926 


Digitized  by  the  Internet  Archive 

in  2011  with  funding  from 

University  of  California,  Davis  Libraries 


http://www.archive.org/details/suggestionsongra07elli 


SUGGESTIONS  ON  GRAPEFRUIT  CULTURE 
IN  IMPERIAL  VALLEY 

EAYMOND  ELLISi 


INTRODUCTION 

Present  Status  of  the  Industry. — The  growing  of  grapefruit  in 
Imperial  Valley  is  an  industry  which  is  in  the  purely  developmental 
stage  at  the  present  time,  but  which  has  a  bright  future  in  so  far  as 
the  production  of  good  quantities  of  desirable  fruit  is  concerned. 
The  acreage  involved  is  increasing  each  year,  most  of  the  development 
having  taken  place  since  1920.  At  the  present  time  there  are  approxi- 
mately 5100  acres  planted,  with  about  1500  acres  bearing.  Of  the 
bearing  acreage  only  about  200  acres  have  reached  maturity.  Growers 
should  receive  some  returns  from  their  young  groves  about  four  years 
after  planting  and  the  production  will  normally  increase  until  the 
trees  reach  full  bearing,  which  is  at  about  twelve  years  of  age. 

Marketing  Situation.— To  date  very  little  Imperial  Valley  grape- 
fruit has  been  shipped  outside  of  California,  the  larger  cities  of  this 
state  absorbing  a  large  percentage  of  the  production.  The  time  is  fast 
approaching,  however,  when  new  markets  will  have  to  be  developed 
and  the  people  educated  to  the  high  quality  of  the  desert  grown  fruit. 
This  campaign  of  education  can  best  be  carried  on  by  actually 
placing  the  fruit  in  new  markets  and  in  that  way  creating  a  demand 
for  it. 

There  is  no  reason  to  believe  but  that,  with  high-quality  fruit, 
raised  on  medium-priced  land,  with  cheap  water,  low  fertilizer  costs, 
and  practically  no  expense  for  insect  pest  and  disease  control — the 
growers  of  Imperial  Valley  can  compete  with  any  other  citrus  section, 
especially  in  the  markets  west  of  the  Mississippi  River. 

SOILS   FOR  GRAPEFRUIT 

Selection  of  Land. — The  selection  of  a  suitable  piece  of  land  is  one 
of  the  first  and  most  important  problems  which  the  prospective  grower 
is  called  upon  to  face.  Although  citrus  fruits  will  do  well  on  a  fairly 
wide  range  of  soil  types,  there  are  certain  ideals  toward  which  it  is 
well  to  work,  as  well  as  conditions  to  be  avoided.  The  ideal  soil  is  a 
sandy  loam,  reasonably  free  from  alkali,  having  good  underground 
drainage  and  containing  a  good  supply  of  plant  foods.  The  very 
heavy  soil  types  which  contain  a  high  percentage  of  injurious  salts 
should  be  avoided. 

1  Assistant  in  Agricultural  Extension. 


2  CALIFORNIA   AGRICULTURAL   EXTENSION   SERVICE  [ClRO.  7 

Land  which  has  grown  alfalfa  for  three  or  more  years  is  desirable, 
especially  from  the  standpoint  of  soil  fertility.  A  good  stand  of 
alfalfa  is  also  an  indication  of  low  alkali  content,  and  shows  as  well 
the  possibility  of  good  root  penetration  and  distribution. 

Soil  Types. — The  Holtville  series  of  soils^  is  the  best  suited  to 
grapefruit  culture,  of  those  found  in  Imperial  Valley.  This  series  is 
made  up  of  a  medium  to  heavy  surface  soil  underlain  at  varying 
depths  by  a  sandy  subsoil.  This  last  feature  is  desirable  from  the 
standpoint  of  efficient  drainage.  The  Meloland  series  is  also  suitable, 
being  composed  of  a  light  surface  soil,  underlain  by  a  stratum  of 
heavier  materials.  The  presence  of  this  heavy  layer  sometimes  causes 
trouble,  especially  where  there  is  a  tendency  to  over-irrigate.  The 
Rositas  series  is  also  used  considerably  and  is  suitable,  although  not 
found  in  as  large  bodies  as  the  two  first  mentioned.  This  series  is  of 
lighter  texture  and  requires  the  addition  of  much  organic  matter  for 
best  results. 

There  are  numerous  other  minor  soil  types  and  phases  which  are 
suitable,  but  the  three  mentioned  are  the  ones  of  major  importance. 

The  Imperial  series  is,  generally  speaking,  not  so  well  suited  and 
should  be  avoided.  This  series  is  made  up  of  solid  columns  of  heavy 
soil,  varying  from  a  heavy  clay  loam  to  a  very  heavy  clay  and  gener- 
ally contains  a  considerable  amount  of  objectionable  salts. 

Precautions  in  Handling  Imperial  Valley  Soils. — Citrus  growers 
should  use  great  care  in  handling  any  of  the  Valley  soils,  especially 
the  heavier  types  which  contain  much  silt.  If  cultivated  too  wet  or 
too  dry  a  cloddy  condition  will  result,  and  if  irrigated  too  fast  proper 
penetration  of  moisture  is  not  secured.  Over-irrigation  and  water- 
logging must  be  watched  very  closely  on  those  soil  types  which  are 
underlain  by  strata  of  heavier  materials.  The  prospective  grower 
should  never  think  of  planting  trees  until  a  study  has  been  made  of  the 
various  underlying  strata  of  his  soil ;  observation  made  on  rapidity  and 
depth  of  water  penetration;  and  whether  or  not  there  is  any  indi- 
cation of  a  rising  water  table.  This  investigation  can  be  made  very 
easily  with  a  soil  auger. 

Alkali. — Practically  every  tract  of  land  in  Imperial  Valley  con- 
tains considerable  white  alkali  or  other  salts,  which  if  allowed  to 


2  Soil  surveys  describing  soils  in  the  Imperial  Valley,  and  containing  maps 
showing  their  occurrence  can  be  obtained,  by  request,  from  Division  of  Soil 
Technology,  University  of  California,  Berkeley,  California.  Surveys  are  available 
for  the  Brawley  Area,  the  El  Centre  Area,  and  the  Palo  Verde  Area.  Grapefruit 
is  grown  in  Palo  Verde  Valley,  although  that  district  is  not  discussed  in  this 
circular. 


1926]      SUGGESTIONS  ON  GRAPE  FRUIT  CULTURE  IN  IMPERIAL  VALLEY  3 

accumulate  around  the  roots  of  the  trees,  will  cause  trouble.  The 
danger  point  of  concentration  has  not  been  determined,  as  it  depends 
on  the  soil  type  and  the  nature  of  the  salt  mixture. 

SELECTION  OF  STOCK 

Variety. — The  Marsh  seedless  grapefruit  is  the  most  popular 
variety  because  of  a  market  demand  for  a  seedless  fruit.  It  develops 
a  high  sugar-acid  ratio  in  this  region,  earlier  than  in  the  cooler  dis- 
tricts, and  for  that  reason  has  developed  a  special  reputation  in 
Pacific  Coast  markets  as  a  fruit  of  high  quality  in  early  season. 

Type  of  Tree. — The  prospective  grower  should  exercise  great  care 
in  the  selection  of  his  young  trees,  in  order  to  insure,  if  possible,  a 
uniform  grove,  with  each  tree  producing  a  good  crop  of  high-quality 
fruit.  An  investigation  of  the  source  of  the  buds  used  is  advisable, 
and  is  a  point  which  should  not  be  overlooked.  These  buds  should 
be  inserted  on  good  thrifty  seedlings.  All  factors  being  considered, 
the  sour  orange  seedling  is  the  most  satisfactory,  with  the  sweet  orange 
and  pomelo  root  also  iairly  good.  All  trees  should  be  budded  high, 
preferably  six  to  eight  inches  above  the  ground,  in  order  to  preclude 
any  possibility  of  disease  which  might  develop  from  contact  between 
the  soil  and  the  grapefruit  scion. 

Quarantine  Regulations. — Inasmuch  as  Imperial  Valley  is  free 
from  all  scale  insects,  except  the  unimportant  cottony  cushion  scale, 
it  is  to  be  hoped  that  all  growers  will  take  every  precaution  to  prevent 
the  introduction  and  spread  of  these  pests.  Before  importing  any 
trees,  it  is  advisable  to  get  in  touch  with  the  County  Horticultural 
Commissioner  and  get  the  latest  quarantine  regulations.  These  regu- 
lations should  be  obeyed  to  the  letter  if  trouble  is  to  be  avoided  and 
the  citrus  industry  of  the  Valley  kept  on  a  permanent  basis.  In  case 
any  insect  pests  are  found  in  Valley  groves,  they  should  be  eradicated 
at  once. 

PLANTING 

Date  of  Planting. — Planting  time  in  Imperial  Valley  corresponds 
very  closely  wdth  that  of  other  citrus  districts  of  California,  except 
that  the  high  summer  temperatures  make  summer  planting  impossible. 
The  best  planting  date  is  March  15  to  May  1,  inclusive.  Fall  planting 
has  been  found  not  satisfactory. 

Preparation  of  Soil. — Land  which  is  to  be  planted  to  citrus  fruits 
ought  to  be  thoroughly  plowed  during  the  fall  or  winter  previous  to 
planting.  This  is  especially  true  of  old  alfalfa  land,  as  it  gives  the 
material  which  is  plowed  under  a  chance  to  decompose  before  planting 


4  CALIFORNIA   AGRICULTURAL  EXTENSION   SERVICE  [CiRC.  7 

time.  After  plowing,  the  land  can  be  harrowed  or  disced  and  floated 
to  proper  grade  for  irrigation.  High  or  low  spots  must  be  eliminated 
before  planting  as  it  is  almost  impossible  to  do  satisfactory  retouch- 
ing after  the  grove  has  been  planted. 

Laying  OtU  the  Grove. — Apparently  the  trees  should  be  set  at 
least  twenty-four  feet  apart  each  way,  in  order  to  insure  ample  work- 
ing space  when  they  are  grown.  In  laying  out  the  tract  for  planting, 
a  planting  wire  with  markers  soldered  on  it  is  very  useful.  The 
markers  are  placed  on  the  wire  at  whatever  distance  the  trees  are  to 
be  set.  This  wire  is  stretched  across  the  field  and  a  stake  set  at  each 
marker  where  the  trees  will  later  be  planted. 

The  laying  out  and  digging  of  the  holes  should  be  done  at  least 
two  weeks  before  planting.  This  gives  the  soil  around  the  holes  a 
chance  to  become  well  aerated.  Holes  are  dug  at  each  one  of  the 
stakes,  with  the  center  of  the  hole  at  approximately  the  position  of 
the  stake.  Each  man  who  is  digging  carries  with  him  an  extra  supply 
of  pegs  as  well  as  a  small  planting  board,  about  four  feet  long,  with 
a  notch  at  each  end  and  one  in  the  center.  The  center  notch  is  placed 
over  the  stake  which  has  previously  been  set  and  then  pegs  are  driven 
in  the  two  end  notches.  The  board  and  center  stake  are  then  removed 
and  the  hole  dug.  Holes  should  be  about  two  feet  in  diameter  and 
about  the  same  depth. 

Setting  the  Trees. — When  trees  arrive  from  the  nursery  it  is 
imperative  that  they  either  be  planted,  or  placed  where  they  can  be 
supplied  with  water.  Loss  of  moisture  takes  place  very  rapidly, 
especially  when  the  wind  is  blowing,  and  a  great  deal  of  damage  may 
be  done  if  the  trees  are  not  cared  for  immediately. 

When  planting  is  going  on,  the  same  planting  board  which  was 
used  at  digging  time  is  again  carried.  The  board  is  placed  over  the 
two  stakes,  and  the  tree  set  in  the  hole  with  its  trunk  in  the  center 
notch  of  the  planting  board.  This  insures  a  straight  line  of  trees. 
If  the  hole  is  too  deep  it  should  be  filled  in  with  moist  surface  soil 
and  not  with  grain,  straw,  fertilizer,  or  any  other  material  which 
might  damage  the  young  tree  roots.  The  tree  should  be  set  about 
two  inches  higher  than  it  was  in  the  nursery  so  that  settling  will  be 
allowed  for.  Where  balled  trees  are  used  it  is  advisable  to  cut  the 
sacking  at  the  top  and  let  it  fall  back  into  the  hole  and  the  ball  broken 
slightly.  With  bare  rooted  trees,  all  broken  or  deformed  roots  should 
be  removed  before  setting. 

Planters  ought  to  have  a  stream  of  water  following  them  closely 
at  all  times  and  after  each  tree  is  set  and  the  soil  thoroughly  tamped 
around  it,  the  water  should  be  turned  in  and  the  roots  and  soil  around 


1926]      SUGGESTIONS  ON  GRAPE  FRUIT  CULTURE  IN  IMPERIAL  VALLEY  5 

them  given  a  good  soaking.  Too  much  emphasis  cannot  be  placed  on 
proper  firming  of  the  soil  around  the  tree  in  order  to  secure  a  proper 
contact  between  the  roots  and  soil.  This  firming  should  be  done  before 
the  water  reaches  the  tree. 

Balled  vs.  Bare  Boot  Trees. — Generally  speaking  balled  trees  are 
the  more  satisfactory  under  Valley  conditions.  Drying  out  of  the 
root  system  is  not  so  apt  to  take  place  and  the  hazards  of  planting 
are  not  so  great,  providing  the  operations  are  properly  carried  out. 
There  are  some  things  to  be  said  in  favor  of  bare  rooted  trees,  however. 
In  the  first  place  it  allows  for  an  inspection  of  the  root  system  and 
the  removal  of  undesirable  roots,  as  well  as  doing  away  with  the 
payment  of  freight  charges  on  large  quantities  of  soil.  Provided  the 
grower,  himself,  is  to  superintend  the  planting  operations,  and  with 
weather  conditions  just  right,  then  bare  rooted  trees  may  be  used. 

PROTECTION  AGAINST  UNFAVORABLE   CLIMATIC   CONDITIONS 

Wind  and  Windbreaks. — The  prevailing  winds  in  Imperial  Valley 
come  from  the  north  and  west,  reaching  their  greatest  intensity  during 
February,  March  and  April,  and  doing  most  of  their  damage  during 
that  time.  Every  year  growers  lose  heavily  through  partial  defolia- 
tion of  their  trees,  as  well  as  scarring  of  the  fruit,  and  the  resultant 
lowering  of  the  grade.  The  actual  damage  in  dollars  and  cents  is 
hard  to  estimate,  but  it  has  been  officially  stated  that,  of  the  fruit 
entering  the  packing  house  of  the  Imperial  Valley  Citrus  Association 
during  the  1924-25  season,  25  per  cent  was  cull  fruit,  35  per  cent 
second  grade,  and  the  remainder  first  grade.  According  to  the  house 
manager,  90  per  cent  of  the  cull  and  second  grade  fruit  was  so  placed 
because  of  wind  injury.  Add  to  this  the  injury  done  to  the  trees  and 
the  loss  due  to  fruit  being  blown  off  and  one  can  readily  see  the  need 
for  adequate  protection. 

The  best  means  of  protection  is  an  efficient  windbreak  of  some 
variety  of  evergreen  tree.  There  are  several  varieties  of  trees  which 
do  well  in  the  Valley  and  are  also  suitable  for  windbreak  purposes. 
Among  these  is  the  athel  {Tamarix  articulata) ,  a  fast  growing  ever- 
green, well  suited  to  desert  conditions  (see  fig.  1).  It  is  easily  propa- 
gated from  cuttings  and  when  well  cared  for  makes  a  dense  growth 
very  quickly,  even  though  somewhat  low  for  an  ideal  windbreak. 
Some  of  the  varieties  of  eucalyptus  are  also  very  good,  among  these 
being  the  gray  gum  {Eiicalypius  tereticornis) ,  red  gum  (Eucalyptus 
rostrata),  and  blue  gum  (Eucalyptus  globulus).  A  very  effective  and 
desirable  windbreak  is  one  of  eucalyptus  interset  with  athel. 


CALIFORNIA   AGRICULTURAL   EXTENSION    SERVICE 


[CiRC.  7 


Regardless  of  the  variety  of  tree  used,  growers  should  cut  to  a 
minimum  the  competition  between  the  windbreak  and  the  orchard 
trees.  This  can  best  be  accomplished  by  proper  fertilization  and 
irrigation  of  the  windbreak,  as  well  as  a  proper  system  of  root  prun- 
ing. Subsoiling  deeply  between  the  windbreak  and  the  first  row  of 
orchard  trees  is  an  effective  method  of  root  pruning.  This  operation 
should  be  carried  out  at  least  twice  each  year,  with  the  cut  being  made 
at  the  same  place  each  time. 


Fig.  1.— Typical  athel  windbreak. 

Providing  the  grower  is  desirous  of  protecting  his  young  trees,  it 
is  best  to  plant  the  windbreak  at  the  same  time  as  the  grove  is  set  out, 
or  even  before,  depending  on  the  growing  habit  of  the  trees  selected. 
Windbreak  trees  should  be  set  approximately  six  feet  apart  and  then 
as  they  overlap  in  later  years,  part  of  them  may  be  removed.  Plenty 
of  space  must  be  left  between  the  orchard  trees  and  the  windbreak, 
so  that  turning  with  cultivating  tools  and  root  cutting  will  be 
facilitated  and  root  competition  reduced  to  a  minimum. 

Sunburn. — The  protection  of  the  trunks  of  young  trees  from  the 
sun  is  one  of  the  first  considerations  after  planting.  The  young  trees, 
for  the  first  two  or  three  years,  have  no  natural  protection  on  the 
trunks  in  the  way  of  foliage,  consequently  they  must  be  taken  care  of 
artificially.  This  protection  may  be  accomplished  in  several  different 
ways.  Yucca  and  waxed  paper  protectors,  placed  around  the  trunks, 
are  very  effective,  but  are  not  used  very  largely  because  they  create 
a  harbor  for  insects  which  often  damage  the  young  trees.  Whitewash 
is  also  good  and  is  to  be  recommended  under  Valley  conditions.     It 


1926]      SUGGESTIONS  ON  GRAPE  FRUIT  CULTURE  IN  IMPERIAL  VALLEY  7 

scales  off  to  some  extent,  but  by  getting  a  good  mixture  and  making 
two  or  three  applications  during  the  summer,  very  satisfactory  results 
can  be  obtained. 

Several  mixtures  of  whitewash  may  be  used.  Cold  water  paint, 
a  white  powder  much  like  kalsomine,  is  very  good  because  of  its 
tendency  to  stick  to  the  tree  trunks.  This  powder  should  be  mixed 
with  water  until  a  thick,  creamy  mixture  is  obtained. 

A  formula  made  up  of  ten  pounds  of  quicklime  and  three  pounds 
of  sulfur  has  also  proved  satisfactory.  The  quicklime  should  be  slaked 
with  water  and  the  sulfur  added  while  the  heat  is  being  given  off. 
The  mixture  must  be  cool  before  being  applied  to  the  tree. 

The  maintenance  of  a  good  coat  of  tree  whitewash  throughout  the 
first  two  or  three  years  is  a  task,  but  is  undoubtedly  worth  while,  not 
only  from  the  standpoint  of  tree  protection,  but  also  because  it  fur- 
nishes opportunity  for  better  acqaintance  with  individual  trees. 

Frost. — The  hazard  of  freezing  temperatures  is  considerable  in 
the  Valley,  especially  with  reference  to  the  young  trees.  Fruit  is  also 
damaged  at  times  and  considerable  loss  sustained  by  some  growers. 
During  the  winter  of  1924-25  this  was  especially  true,  as  a  good  part 
of  the  fruit  which  remained  on  the  trees  at  the  time  of  the  low 
temperatures  was  lost.  Although  young  trees  are  often  damaged 
considerably  by  cold  weather,  the  mature  trees,  providing  they  are 
in  a  healthy  condition,  are  very  seldom  affected  to  any  great  extent. 
Sometimes  a  few  leaves  and  small  branches  are  lost,  but  the  recovery 
is  rapid  with  the  advent  of  warm  weather.  The  cold  waves  which 
visit  Imperial  Valley  correspond  very  closely  to  those  in  other  parts 
of  southern  California,  both  as  to  duration  and  intensity. 

Growers  should  be  concerned  largely  with  bringing  their  groves 
through  the  first  three  years  as  that  is  the  critical  period  in  so  far  as 
frost  damage  is  concerned.  There  are  several  rules  to  follow  if  this 
damage  is  to  be  reduced  to  a  minimum.  The  trees  must  be  kept 
healthy  through  proper  moisture  supply  and  soil  fertility,  as  well 
as  free  from  insect  pests  and  diseases. 

Providing  the  trees  are  in  good  physical  condition,  the  problem 
then  resolves  itself  into  one  of  protecting  the  small  tree  trunks  with 
some  such  insulating  material  as  cornstalks,  tules,  or  arrow  weed 
(see  fig.  2).  This  material,  a  bundle  about  ten  inches  in  diameter, 
should  be  set  in  place  during  the  latter  part  of  November  and  left 
on  until  about  the  first  of  March.  It  is  imperative  that  the  bundle  be 
tied  snugly  around  the  tree  trunk,  once  near  the  ground,  again  half- 
way up  the  trunk,  and  a  third  time  just  below  the  head  of  the  tree. 


8 


CALIFORNIA    AGRICULTURAL   EXTENSION    SERVICE 


[CiRC.  7 


The  wrapping  material  is  allowed  to  go  up  through  the  head  of  the 
tree  in  order  to  protect  the  main  framework  branches,  but  no  attempt 
should  be  made  to  pull  the  foliage  inside  the  bundle. 

The  tree  and  its  protecting  material,  during  the  first  winter  at 
least,  should  be  staked  to  prevent  blowing  over  by  the  wind.  Ordinary 
redwood  grape  stakes  are  very  satisfactory  for  this  purpose.  The 
stakes  are  driven  into  the  ground,  preferably  on  the  west  side,  after 
the  insulating  material  has  been  set  in  place.  The  tree  and  bundle 
need  to  be  tied  to  the  stake  in  only  one  place,  that  being  as  high  up 
on  the  tree  as  possible. 


Fig.  2. — Showing  proper  method  of  protecting  young  tree  trunks   from 
frost  damage.    Note  stake  to  prevent  blowing  over. 


The  initial  cost  to  growers  for  this  system  of  protection,  including 
stakes,  wrapping  material  and  labor,  will  be  approximately  ten  cents 
per  tree.  The  exact  cost  will  depend  largely  on  the  kind  of  stakes 
used  and  the  speed  with  which  the  work  is  done. 

It  remains  to  be  seen  whether  or  not  Imperial  Valley  growers  will 
install  orchard  heating  systems  when  these  young  groves  come  into 
bearing.  A  careful  study  of  the  economics  of  the  situation  should  be 
made  showing  a  comparison  of  the  annual  losses  sustained,  with  the 
cost  of  installing  and  maintaining  an  adequate  heating  system.^ 

3  Figures  on  costs  of  orchard  heating  have  been  given  in  California  Agr.  Exp. 
Sta.  Bui.  398,  Orchard  Heating  in  California,  by  Warren  E.  Schoonover  and 
Eobert  W.  Hodgson,  in  cooperation  with  Floyd  D.  Young  of  the  United  States 
Weather  Bureau. 


1926]      SUGGESTIONS  ON  GRAPE  FRUIT  CULTURE  IN  IMPERIAL  VALLEY 


IRRIGATION 

The  proper  irrigation  of  a  citrus  grove  is  an  important  operation, 
especially  in  a  region  where  the  average  annual  rainfall  is  about  three 
inches  and  the  evaporation  very  high.  Irrigation  does  not  mean  the 
application  of  great  quantities  of  water  at  regular  stated  intervals,  but 
is  rather  the  judicious  wetting  of  the  root  zone  at  such  times  as  the  tree 
needs  it.  This  does  not  mean  that  it  is  either  necessary  or  desirable 
to  have  the  soil  kept  evenly  wet.  On  the  other  hand,  it  seems  that  the 
trees  do  better  if  the  soil  moisture  fluctuates  from  very  wet  to  very 


Fig.  3. — Showing  furrow  irrigation,  using  only  two  inside  furrows. 

near  the  wilting  point.  Trees  should  not  be  allowed  to  suffer  for 
water,  but  soil  aeration  is  facilitated  as  the  moisture  content  grows 
less,  and  as  a  consequence  root  growth  is  benefited  and  the  tree 
invigorated,  providing  the  soil  does  not  become  too  dry. 

Very  early  in  the  life-history  of  the  grove,  the  owner  should  make 
a  study  of  his  soil  with  reference  to  water  penetration  and  holding 
capacity.  On  this  study  will  be  based  the  frequency  and  amount  of 
water  to  be  applied,  length  of  run,  size  of  head  and  to  some  extent  the 
method  of  application.  This  study  can  be  made  by  cutting  trenches 
across  the  irrigation  furrows  and  also  by  the  use  of  a  soil  auger. 

The  system  of  irrigation  to  be  used  will  depend  to  some  extent  on 
the  soil  type  as  well  as  on  the  age  of  the  grove.  With  young  trees 
it  is  not  necessary  to  wet  all  of  the  soil  between  the  tree  rows  at  every 
irrigation.  Two  furrows,  one  on  each  side  of  the  row,  may  be  used 
for  four  or  five  irrigations  (see  fig.  3).  The  entire  area  should  be 
thoroughly  wet  two  or  three  times  during  the  year.     A  combination 


10 


CALIFORNIA   AGRICULTURAL   EXTENSION   SERVICE 


[CiRC.  7 


of  furrow  and  flood  irrigation  is  especially  desirable  where  there  is 
any  amount  of  objectionable  salts  or  alkali  present.  Flooding  is  not 
so  desirable  as  a  general  practice,  but  can  be  used  to  good  advantage 
to  redistribute  any  of  the  salts  which  might  be  present.  Flooding  can 
be  done  at  almost  any  time  of  the  year,  but  preferably  in  the  winter. 


Fig.  4. — Showing  after  effects  on  soil  of  flood  irrigation. 
Note  center  border. 


It  is  best  done  by  throwing  up  a  border  midway  between  the  tree  rows 
and  running  the  water  between  the  borders  and  directly  down  the  tree 
row  (see  fig.  4). 

Groves  planted  on  the  sandier  soil  types  are  best  not  flood  irri- 
gated, as  these  soils  have  a  tendency  to  take  too  much  water.  This 
not  only  causes  a  waste  of  water,  but  also  may  cause  trouble  from  a 


1926]      SUGGESTIONS  ON  GRAPE  FRUIT  CULTURE  IN  IMPERIAL  VALLEY  11 

local  water  table,  especially  if  there  is  a  heavy  subsoil  present.  The 
sandier  soils,  as  a  general  rule,  do  not  contain  any  great  amount  of 
alkali,  so  that  flooding  is  not  necessary  from  the  standpoint  of 
redistribution  of  salts. 

CULTIVATION 

Cultivation  to  conserve  soil  moisture  is  important  only  in  so  far 
as  it  controls  weeds  or  eliminates  large  cracks  in  the  soil.  If  culti- 
vation is  done  at  the  proper  time,  soil  aeration  is  helped  to  some 
extent.  It  is  not  necessary  to  cultivate  the  grove  after  each  irrigation. 
On  the  other  hand,  it  seems  desirable  that,  at  least  three  or  four  times 
each  year,  the  grove  be  left  uncultivated  between  irrigations,  so  that 
the  soil  will  dry  out  and  crack,  thus  permitting  the  entrance  of  fresh 
air  into  the  soil  as  well  as  assisting  the  water  penetration  at  the  next 
irrigation.  This  practice  is  to  be  especially  recommended  on  the 
heavy  soil  types. 

Practically  all  of  the  Imperial  Valley  soils  contain  large  amounts 
of  such  very  fine  materials  as  silt  and  clay,  consequently  must  be 
handled  with  great  care.  If  plowed  when  either  too  wet  or  too  dry, 
huge  clods  will  be  turned  up  and  if  disced  or  shallow-cultivated  when 
too  wet,  an  impervious  plowpan  may  be  formed.  The  proper  time  at 
which  to  cultivate  is  an  individual  problem  and  must  be  studied  by 
each  grower.  It  is  .not  necessary  to  take  so  many  precautions  with 
the  sandier  soil  types. 

MAINTENANCE  OF  SOIL   FERTILITY 

The  Imperial  Valley  citrus  grower  should  adopt  and  follow  an 
adequate  fertilizer  program  from  the  very  first  if  best  results  are  to 
be  obtained.  Nitrogen  is  the  element  which  is  most  likely  to  be 
deficient  in  the  Valley  soils,  and  any  program  adopted  should  provide 
especially  for  the  addition  of  this  element. 

Cover  Crops. — During  the  first  three  or  four  years,  while  there  is 
considerable  space  between  the  trees,  soil  fertility  can  best  be  main- 
tained by  means  of  leguminous  cover  crops.  These  crops  may  be 
grown  either  in  summer  or  winter,  or  both  if  the  land  is  none  too 
fertile.  The  grower  has  a  number  of  satisfactory  legumes  from  which 
to  choose.  It  is  desirable  that  one  be  selected  which  is  deep  rooting, 
especially  on  the  heavier  soils.  Production  of  a  large  tonnage  of 
green  tops  is  also  desirable. 

Among  the  winter  crops  which  are  satisfactory,  are  the  garden 
pea,  sour  clover  {Melilotus  indica),  and  berseem  or  Egyptian  clover. 


12  CALIFORNIA   AGRICULTURAL   EXTENSION   SERVICE  [ClRC.  7 

The  first  named  is  very  good,  as  it  not  only  serves  as  a  cover  crop, 
but  also  promises  some  financial  return,  providing  it  is  planted  early 
in  the  fall  and  a  normal  year  encountered  (see  fig.  5). 

Some  of  the  summer  legumes  which  are  satisfactory  are  sesbania 
(wild  hemp),  Brabham  and  Iron  cowpeas,  and  several  varieties  of 
soybeans.  All  of  these  produce  good  tonnages  of  green  tops  and  root 
deeply.  Where  a  summer  crop  is  grown  the  grower  should  watch  his 
soil  moisture  conditions  very  closely,  so  that  no  competition  for  water 
takes  place  between  the  trees  and  the  cover  crop.  This  holds  true  for 
a  winter  crop,  also,  but  to  a  lesser  extent. 


Fig.  5. — Winter  cover  crop  of  garden  peas  in  young  grapefruit  grove. 

Other  Fertilizers. — When  the  trees  have  grown  to  such  a  size  as  to 
cut  down  materially  the  available  growing  space  for  cover  crops,  then 
other  fertilizers  must  be  used.  Organic  matter  is  always  necessary, 
so  that  manure,  bean  straw  or  alfalfa  hay  should  be  used.  The 
amount  to  be  applied  will  depend  on  the  material  and  its  nitrogen 
content.  Sufficient  material  should  be  applied  annually  to  furnish 
each  tree  with  one  to  one  and  a  half  pounds  of  available  nitrogen. 
The  application  of  these  bulky  organics  is  best  made  in  the  early  fall, 
preferably  in  October.  In  order  to  supplement  the  fall  application 
of  organic  matter,  a  quickly  available  nitrogenous  commercial  fer- 
tilizer should  be  used  in  the  early  spring.  An  additional  pound  of 
available  nitrogen  per  tree  should  be  added  in  this  way. 

The  above  outlined  program  should  care  for  the  ordinary  grove 
and  keep  its  production  at  a  good  level,  providing  other  conditions 
are  normal.* 


4  Further  information  bearing  on  special  conditions  may  be  found  in  California 
Agr.  Exp.  Sta.  Cir.  283,  Fertilizing  Citrus  Trees  in  California,  by  Eobert  W. 
Hodgson. 


1926] 


SUGGESTIONS  ON  GRAPE  FRUIT  CULTURE  IN  IMPERIAL  VALLEY 


13 


PEST  CONTROL 


Cottony  Cushion  Scale. — The  pest  control 
problem  among  citrus  growers  of  Imperial 
Valley  is  as  yet  comparatively  simple.  None 
of  the  scale  insects  so  common  in  other  citrus 
districts  have  yet  been  introduced,  except  the 
cottony  cushion  scale.  There  are  several  infes- 
tations of  this  insect,  but  it  can  be  controlled 
by  the  use  of  the  Australian  ladybird,  which 
feeds  upon  it.  These  ladybirds  may  be  secured 
on  application  to  the  County  Horticultural 
Commissioner. 

Fire  Ant. — The  fire  ant  {Solenopsis  gemi- 
nata)  is  the  most  important  of  the  insects  at- 
tacking citrus  trees  in  this  region.  This  is  a  small 
red  ant  which  appears  with  the  warm  weather 
in  late  spring  or  early  summer,  and  works  only 
on  the  young  trees.  The  ants  make  their  nests 
among  the  roots  of  the  small  trees,  coming  out 
onto  the  limbs  and  trunks  to  feed  on  any  fresh 
sap  which  might  break  out  over  the  tree.  They 
not  only  feed  on  the  sap,  but  eventually  start 
to  work  on  the  tender  bark  and  if  left  un- 
molested for  a  few  days  will  completely  girdle 
a  young  tree  (see  fig.  6). 

Certain  control  measures  can  be  recom- 
mended which,  if  followed,  will  materially 
lessen  the  danger  from  these  insects.  Tree 
whitewash  is  preferable  to  protectors,  because 
it  does  not  afford  a  harbor  behind  which  the 
ants  can  work.  The  application  of  two  or  three 
coats  of  whitewash  also  gives  the  grower  the 
occasion  to  inspect  each  individual  tree  for 
evidences  of  any  damage. 

When  an  ant  nest  is  found,  the  application 
of  two  or  three  teaspoonfuls  of  calcium  cyanide 
dust  or  flakes  around  the  base  of  the  tree  will 
destroy  a  large  percentage  of  the  ants.  This 
material  should  be  placed  at  least  two  inches 
away  from  the  tree  trunk  and  on  the  surface  of 


Fig.  6. — Damage  to 
young  grapefruit  shoot 
by  fire  ant. 


14  CALIFORNIA   AGRICULTURAL   EXTENSION    SERVICE  [CiRC.  7 

the  ground.  Infested  trees  should  be  marked,  and  at  the  next  irri- 
gation, which  should  not  be  sooner  than  twenty-four  hours  after  the 
application  of  cyanide,  the  irrigator  should  cut  the  water  in  around 
these  trees  and  drown  out  any  of  the  remaining  ants. 

Tree  tanglefoot  has  been  used  to  good  advantage  by  some  growers, 
but  with  the  advent  of  cool  nights  the  material  has  a  tendency  to 
harden  and  lose  its  effectiveness. 

Tlirips. — There  are  several  species  of  thrips  found  in  Imperial 
Valley,  chief  among  them  being  the  grain  thrips.  This  insect  is  often 
found  on  the  citrus  trees,  but  is  of  little  economic  importance  to  the 
growers  because  the  damage  done  by  it  is  negligible.  However,  some 
growers  are  desirous  of  trying  control  measures  at  times,  in  which  case 
a  2  per  cent  lime-sulfur  solution  may  be  used  experimentally.  This 
solution  should  be  applied  as  a  spray  at  blooming  time. 

DISEASES 

None  of  the  diseases  common  to  citrus  trees  are  of  any  importance 
in  Imperial  Valley,  except  possibly  brown  rot  gummosis  {Phythiacistis 
citrophtho7^a) .  Even  this  is  of  little  importance  under  the  existing 
weather  conditions.  It  develops  best  in  a  cooler,  more  humid  environ- 
ment. However,  it  is  found  occasionally,  but  can  be  cured  rather 
easily  by  cutting  out  the  diseased  portion  and  applying  some  dis- 
infectant such  as  Bordeaux  paste  or  a  good  whitewash.  This  disease 
always  appears  on  the  lower  part  of  the  trunk  and  is  characterized 
by  the  presence  of  a  rather  dark  colored  gum.  Under  no  circum- 
stances should  growers  confuse  this  disease  with  the  light  colored  gum 
often  found  on  the  trunk  and  limbs  of  young  trees.  This  latter  is 
not  a  disease,  but  is  probably  due  to  improper  soil  moisture  conditions, 
and  should  cause  no  worry  except  that  ants  may  be  attracted  by  the 
fresh  sap. 

PRUNING 

General  Pruning. — The  pruning  of  healthy,  growing  trees  is  a  very 
minor  operation.  After  being  properly  headed  when  young,  it  should 
not  be  necessary  to  touch  them  for  at  least  four  years.  After  the  trees 
come  into  bearing,  there  will  be  some  pruning  to  do  each  year.  Dead 
wood  and  interfering  branches  are  best  removed.  If  the  tree  is  very 
dense,  a  small  amount  of  leaf  surface  should  be  removed,  in  order  to 
admit  more  air  and  sunlight  and  thus  promote  the  growth  of  more 
inside  fruit.  The  removal  of  any  leaf  surface  should  be  done  in  the 
winter  time,  when  the  trees  are  as  nearly  dormant  as  possible.  Growers 


1926] 


SUGGESTIONS  ON  GRAPE  FRUIT  CULTURE  IN  IMPERIAL  VALLEY 


15 


should  not  remove  too  much  growth  from  the  south  side  of  any  tree, 
as  sunburning  of  the  trunk  or  main  framework  branches  might  result. 
Water  sprouts  coming  on  the  trunk  and  main  framework  branches 
ought  to  be  removed  when  small,  so  that  the  resultant  wounds  will  be 
of  minor  importance  and  will  heal  quickly. 


Fig.  7  Fig.  8 

Fig.  7. — Young  grapefruit  tree  before  pruning  out  dead  wood  and  suckers, 
after  being  frozen. 

Fig.  8. — Same  as  figure  7,  after  pruning. 

Special  Pruning  for  Frost  Injured  Trees. — Occasionally  trees  are 
severely  injured  by  low  temperatures  and  require  special  treatment 
during  the  following  year.  This  applies  to  young  trees,  especially,  as 
none  of  the  older  ones  have  as  yet  been  injured  to  any  extent  by  cold 
weather.  This  treatment  should  consist  only  of  proper  irrigation  and 
cultivation  for  two  or  three  months  after  the  removal  of  the  protecting 
materials.  Care  must  be  taken  not  to  over-irrigate,  as  the  new  growth 
should  be  as  healthy  as  possible.  In  those  cases  where  all  the  foliage 
has  been  frozen  but  the  trunk  and  main  framework  branches  unhurt, 
it  is  best  to  force  growth  as  rapidly  as  possible.  No  pruning  should 
be  done  until  June  or  later.  By  that  time  all  of  the  frosted  wood  will 
have  died  back  and  can  be  removed  (see  figs.  7  and  8).  Any  water 
sprouts  on  the  trunk  may  also  be  removed.    If,  in  the  judgment  of  the 


16  CALIFORNIA   AGRICULTURAL  EXTENSION   SERVICE  [CiRC.  7 

grower,  the  removal  oi  all  the  sprouts  or  suckers  will  be  too  great  a 
reduction  of  leaf  surface  for  the  good  of  the  tree,  some  of  them  may 
be  left  on  until  the  following  winter.  Some  of  them  may  also  be  cut 
half  way  through  and  bent  over  so  as  to  reduce  the  rapidity  of  sap 
flow  and  then  entirely  removed  the  following  fall.  This  practice  is 
known  as  lopping  and  works  to  advantage  in  many  cases.  As  soon  as 
the  protecting  materials  have  been  removed  in  the  spring,  any  exposed 
trunl^s  and  main  branches  should  be  whitewashed  to  prevent  sun- 
burning. 

Oftentimes  trees,  especially  those  in  their  first  year,  are  more 
severely  frozen,  necessitating  either  removal  or  the  building  up  from 
a  new  shoot.  There  seems  to  be  some  advantage  in  this  latter  method-, 
as  the  root  system  is  already  well  established  and  growing.  There 
will  be  some  trees,  however,  which  are  so  severely  frozen  that  the  new 
growth  will  be  weak  and  spindling,  in  which  case  replanting  is  advis- 
able. It  is  not  practical  to  try  to  save  and  rebud  trees  frozen  below 
the  bud  union. 

Kebuilding  a  frosted  tree  from  a  shoot  which  has  arisen  from  the 
trunk,  above  the  bud  union,  can  be  accomplished  by  careful  handling 
and  considerable  work.  All  new  shoots  which  come  out  should  be 
allowed  to  grow  until  about  April,  when  the  most  vigorous  one  is 
selected  and  tied  up  loosely,  either  to  a  stake  or  to  the  old  stump.  This 
is  done  in  order  to  train  the  new  tree  trunk  in  an  upright  habit  of 
growth. 

About  a  quarter  of  the  new  shoots  may  be  removed  in  June  and 
the  remainder  lopped  over  until  the  following  winter,  when  they  can 
be  removed.  It  is  advisable  that  an  extra  shoot  besides  the  one  selected 
be  left,  in  case  the  latter  should  be  broken  off.  This  extra  branch 
may  also  be  removed  during  the  following  winter.  If  possible,  the 
new  tree  trunk  should  be  brought  out  on  the  west  side  of  the  old  one, 
so  as  to  lessen  the  possibility  of  breaking  off  by  the  wind. 

When  the  new  tree  trunk  has  attained  a  height  of  about  three  feet, 
it  should  then  be  headed  back  to  the  desired  height.  When  it  has 
become  strong  enough  to  support  itself,  then  the  old  stump  should 
be  removed  and  the  wound  covered  with  grafting  wax.  Subsequent 
treatment  should  be  the  same  as  for  any  other  young  tree. 

INTERCROPPING   WITH    CASH    CROPS 

Inasmuch  as  there  is  considerable  unused  land  between  the  rows 
of  young  grapefruit  trees,  the  grower  can  sometimes  make  a  part  of 
his  expenses  by  growing  some  cash  crop  between  the  rows.  The  trees 
will  not  be  harmed  in  any  way,  providing  the  grower  always  keeps 


1926]      SUGGESTIONS  ON  GRAPE  FRUIT  CULTURE  IN  IMPERIAL  VALLEY  17 

in  mind  the  fact  that  the  grapefruit  is  the  chief  crop  under  consider- 
ation and  is  guided  accordingly,  especially  in  his  fertilization  and 
irrigation  programs. 

Garden  Peas. — This  crop,  which  was  mentioned  briefly  under 
winter  cover  crops,  is  a  very  satisfactory  and  desirable  intercrop. 
Planted  as  soon  as  the  weather  breaks  in  September,  it  will,  under 
normal  conditions,  produce  a  crop  of  peas  during  the  early  winter. 
These  peas  are  generally  sold  for  a  fair  price  at  that  time  of  the  year, 
thus  returning  to  the  grower  some  of  his  expenses,  as  well  as  building 
.up  the  fertility-  of  the  soil. 


Fig.  9. — Alfalfa  intercrop.     Showing  also  proper  method  of  irrigating 
trees  separately  from  intercrop. 

Alfalfa. — Some  growers  have  used  alfalfa  to  advantage  as  an  inter- 
crop (see  fig.  9).  The  crop  should  be  planted  in  October,  before  the 
grove  is  to  be  set  out.  About  December  the  grower  should  plow 
strips  through  the  alfalfa  for  his  tree  rows.  These  strips  ought  to 
be  at  least  five  to  six  feet  wide.  The  trees  are  then  set  in  the  bare 
strips  during  the  following  spring.  The  alfalfa  may  be  safely  left 
in  the  grove  for  at  least  three  years,  provided  the  strips  are  widened 
each  year,  so  as  to  preclude  any  possibility  of  competition  between  the 
intercrop  and  the  trees. 

Miscellaneous  Cash  Crops. — There  are  a  number  of  non-leguminous 
intercrops  which  may  be  used,  provided  competition  for  water  and 
plant  food  is  cut  to  a  minimum.  Some  of  these  annual  crops  are 
cantaloupes,  lettuce,  watermelons,  tomatoes,  and  corn.  In  the  case 
of  corn  the  stalks  are  later  used  in  frost  protection.  All  of  these  crops 
take  much  plant  food  from  the  soil,  a  point  to  be  borne  in  mind  when 
determining  upon  the  cash  crop.  They  also  are  very  different  from 
the  trees  in  their  fertilizer,  soil  moisture,  and  other  cultural  require- 
ments. However,  they  do  offer  some  promise  of  a  cash  return  each 
year  until  the  trees  come  into  bearing,  and  will  not  injure  the  trees 
if  proper  care  is  taken. 


18  CALIFORNIA   AGRICULTURAL   EXTENSION    SERVICE  [CiRC.  7 


CONCLUSION 

The  future  of  the  grapefruit  industry  in  Imperial  Valley  will 
depend  to  a  large  extent  on  the  growers  themselves.  They  should  not 
expect  the  high  prices  to  continue  which  have  prevailed  during  the 
past  five  years,  especially  after  the  new  acreage  in  Texas,  Florida, 
and  Arizona  comes  into  bearing.  However,  there  is  every  reason  to 
believe  that  the  grower  may  expect  a  fair  profit  on  his  investment, 
providing  the  trees  are  kept  at  a  high  state  of  production  by  means  of 
proper  orchard  practices  and  the  cost  of  operation  kept  at  a  minimum 
by  means  of  good  business  methods.  The  growers  must  also  cooperate 
with  each  other  in  advertising  and  selling  their  product  if  they  are  to 
secure  the  best  results. 


